1. Field of the Invention
This invention relates to the manufacture of prestressed reinforced concrete articles, for example, beams and railway sleepers.
2. Description of the Prior Art
British Pat. No. 1,460,149 describes the simultaneous manufacture of a plurality of pre-stressed concrete articles containing wires, rods or other elongate reinforcing members and the previously proposed method involves the location between two stressing abutments of a series of gangs of moulds which are introduced to the space between the abutments (known as the casting bed), by positioning the gangs of moulds on lifting tables so that once in position between the abutments, the mould gangs can be raised by the lifting tables so as to receive within their cross-sections appropriate lengths of reinforcing wire or other elongate reinforcing members before the insertion of end plates in the moulds. The end plates are arranged to accommodate the reinforcing members without mutual interference.
As it will be understood, the abutments which support the clamped reinforcing wires during the casting and initial curing process of the concrete are required to resist the application of very considerable forces and the total force will be of the order of hundreds of tons, at least, with the consequent requirement that the abutments should be massive and carried by substantial foundations. While the hereinbefore described method has been found to be satisfactory in practice, the requirement to provide a series of lifting tables depending upon the number of gangs which can be accommodated in the casting bed between the abutments has resulted in complication, the cutting of the wires or strands between moulds while they are in the casting bed and high energy use and further it has been found that in practice it is necessary to position all the series of gangs of moulds between the abutments before initiating any concrete pouring because of the time required for each transfer.
One object of the invention is to provide an apparatus and a method for the manufacture of prestressed reinforced concrete articles which is an improvement on the prior art and in particular have lower energy requirements.